Example 4 (with method reference)

Interestingly, if we use a method reference instead, the functionality is exactly the same but we get different bytecode.

public class Example4_method_reference {
    // lambda with method reference
    void example() throws InterruptedException {
        waitFor(new HttpServer(), HttpServer::isRunning);
    }
}

Via the call to LambdaMetafactory when the final execution occurs, method_reference results in a call to invokevirtual rather than invokestatic. The invokevirtual opcode is used to call public, protected an package protected methods so it implies an instance is required. The instance is supplied to the metafactory method and no lambda (or static function) is needed at all; there are no lambda$ in this bytecode.

void example() throws java.lang.InterruptedException;
    descriptor: ()V
    flags:
    Code:
      stack=2, locals=1, args_size=1
         0: new #2 // class Server$HttpServer
         3: dup
         4: invokespecial #3 // Method Server$HttpServer...